Antioxidant properties of Lactobacillus-fermented and non-fermented Graptopetalum paraguayense E. Walther at different stages of maturity

Accumulation of bioactive compounds, during developmental stages of Graptopetalum paraguayense E. Walther, was investigated between 30 and 90 days as a function of physiological maturity. Three distinct phases were defined: immature phase (30 days), intermediate developmental phase (30–60 days), and maturation phase (60–90 days). Gallic acid and quercetin, antioxidative bioactive compounds, were identified as biomarkers for determining the optimum physiological maturity stage in G. paraguayense E. Walther. With regard to the antioxidant activity of G. paraguayense E. Walther at different developmental stages, the results indicated that the leaves of immature G. paraguayense E. Walther had the highest 2,2′-azino-bis(3-ethylbenzothiazoline-6-sulphonate) (ABTS-), superoxide radical-, and 1,1-diphenyl-2-picrylhydrazyl (DPPH·)-scavenging activities. Fermentation of G. paraguayense E. Walther with Lactobacillus plantarum BCRC 10357 significantly increased the level of flavonoids and total phenolics, including quercetin and gallic acid. Total phenols were the major naturally occurring antioxidant components in lactic acid bacteria-fermented G. paraguayense E. Walther.